FROM DUST TO DUST: QUATERNARY WIND EROSION OF THE MU US DESERT AND LOESS PLATEAU, CHINA

In east-central China, the Ordos Basin encompasses the deflationary and most internally-drained Mu Us Desert in the northwest and the fluvially incised Quaternary Chinese Loess Plateau to the south and east. The boundary between the Mu Us Desert and Loess Plateau is an erosional escarpment, up to 400 m in relief, composed of Quaternary loess-paleosol strata. Linear ridges, with lengths ~10²-10³ m, are formed in Mesozoic – Quaternary strata throughout the basin. These ridges are oriented parallel to westerly-to-northerly (clockwise) surface winds that prevail in the basin during modern winter and spring dust storms. These observations suggest that the Loess Plateau previously extended farther to the north and west of its current escarpment margin and has been partially reworked by wind. The linear ridges, internal drainage in the Mu Us Desert, and escarpment retreat are all attributed to wind erosion during Quaternary desert expansion in Asia. The observation that the escarpment roughly coincides with the boundary between fluvial incision and internal drainage suggests that the late Quaternary time-averaged rate of wind excavation and escarpment retreat is in many places on pace with or may exceed that of headward river incision. The resolved surface wind pattern in the Ordos Basin, together with the appreciation of loess recycling by wind, has profound implications for interpretations of loess provenance, grain size, and mineralogy. This study provides evidence that a region of loess accumulation may alternate with, or transform into, one with high wind erosion and dust production rates in response to climatic shifts during the Quaternary.